Airplane propeller



Jan. 17, 1933. e. T. LAMPTON AIRPLANE PROPELLER Filed June 8. 1951 .Jrvvevwm QLEN T. IA MPTON, Y pu2/mim)l- 5M Momma Patented Jan. 17, 1933 PATENT OFFICE GLEN '1. LAMPTON, OI PITTSBURGH, PENNSYLVANIA Amrmnn rnornnmn Application filed June a, 1931. Serial No. 542,734.

This invention relates to improvements in airplane propellers, and has for its object to provide an airplane blade so constructed that natural frequencies of vibration of the blade may be modified and controlled.

It is the object of this invention to provide an airplane propeller in the form of blades which have therein chambers or cavities, partly filled with some granular material or It is particularly the object of this invention to provide an airplane propeller composed of blades having in the tips thereof chambers or cavities containing some fluid material for modifying the natural frequencies of vibration of the blades.

It is my object to reduce the stresses caused by blade vibration beyond the position of equilibrium thereof; and to control the natu-' ral period of vibration of the blades by the use of a predetermined quantity of vibration damping medium.

These and other advantages will appear from the following description taken in connection with the drawing.

Referring to the drawinga Figure 1 is a front elevation of an airplane propeller blade.

Figure 2 is a side elevation of the blade shown in Figure 1. t

Figure 3 is a section through the tip end of one of the blades shown in Figures 1 and 2. Figure 4 is a slightly modified form of blade tip.

In Figures 1 and 2 complete propeller blades for airplanes are shown. The hub of the blade is indicated by the numeral 1, and the blade part is indicated by the numeral 2.

The form and shape of the blade are such as are found in propellers of this type.

Each blade is attached to the hub by means of a clamp 3. Any suitable means may be used for this purpose. The blades are hol- 48 low, composed of some suitable material such as metal. In the form shown in Figure 3 the outer end of each blade has apartition 4 therein attached to the walls of the blades by means of solder 5. This partition forms 50 with the tip end of 'the blade a chamber or cavity for containing a fluid in the form of a liquid or granular solid.

In the body of the blade, adjacent the partition 4, is a vent hole 6. This hole may-be closed or it may be left open. Adjacent the vent hole 6 but extending into the chamber is a charging hole 7, through which the fluid or granular material passes into the cham ber. After the chamber has been properly supplied with fluid or granular material this hole is filled up by some suitable means, either by solder, welding or by a plug.

The damping medium, consisting of liquid or granular material, is indicated by the numeral 8 and extends up to the level in Fig. ure 3, indicated by the reference character 9. It is obvious from an examination of this figure that the cavity or chamber is about four-fifths or five-sixths full. The

amount of material in the cavity may be va- -ried to suit the needs and conditions of the particular blade in which the material is to be placed.

Instead of having the partition or diaphragm as shown in Figure 3 there may be formed an independent and separate container 10 of the same general form and shape as the tip of the blade. This container is shown in Figure 4 and is inserted in the tip of the blade. This container has a charging 80 opening 11, through which the granular material or the fluid or liquid is charged. This container is only partially filled, as is indicated by the reference character 9. This container is formed, filled and closed before insertion in the end of the propeller blade. The other parts of the blades are in all respects similar to that shown in connection with the blade of Figure 3. This blade has the same vent hole 6 and the same blade shape.

Some of the outstanding advantages of this form of propeller blade are as follows: The noise produced by the propeller blades is reduced by reducing the mechanical vibration of the blades. The stress caused by blade vibration beyond the position of equilibrium is reduced. It is possible to control the natural period of vibration of the blades by the use of a predetermined quantity of the vibration damping medium; that is, the

cavity or chamber in the tip of the blade may be more or less completely filled. If the blade tip is completely filled there is no dis lacement. or movement of the imaterial Wit is the chamber,but by not completely filling the chamber a more or less flux or movement in the material takes place so that there is a regulation and a control of the blade,

vibration due to this natural flux and move ment of the material in the chamber.

In order to prevent the material Within the chamber from freezing some low freez- 7 ing liquid or fluid, such as alcohol, is used, or some granular material, such as sand, that s not affected by temperature conditions.

Ethylene glycol may be used as a liquid having a high boiling point.

I desire to comprehend Within my invention such modifications as may be embraced Within my claims and the scope of my invention.

Having thus fully described my invention, What I claim as new and desire tosecure by Letters Patent, is:

1. In an aircraft propeller, a blade having a chamber therein, a sealed container in said chamber, and a fluid partly filling the container for damping the vibration ofthe blade, said container being of such shape as to allow liquidto cover substantially the entire inner surface of the blade tip.

2. In an aircraft propeller, a blade having a closed chamber in its tip and having a fluidtight partition closing the end of the blade from the remainder of said blade, and a predetermined quantity of vibration damping fluid in said chamber for modifying the natural frequencies of the blade vibration to any desired value. or

3. In an aircraft propeller,ra blade having a closed chamber in the tip thereof, including.

a partition extending across the blade near the end thereof and aJfiuid material of high boiling point in said chamber so that the vapor pressure in the chamber shall be a minimum.

In testimony whereof, I aifix my signature.

GLEN T. LAMPTON. 

